The present invention relates to a cyclic or periodic analog signal processing circuit.
More specifically, the processing according to the invention is directed at signals produced by a plurality of sensors or transducers, each of which supplies a shaped measuring signal V.sub.M =KV.sub.R .theta. in which K is a constant, V.sub.R a cyclic reference signal supplying the transducer and .theta. the information to be measured corresponding to a linear or angular displacement.
Linear variometers or linvars produce such signals. They constitute variable coupling transformers whose induced voltage is a linear function of the positioned information .theta. to be measured. The latter corresponds to an angular displacement of the rotor in the case of construction in the form of a rotating machine. There are also constructions with linear displacement, for example of a core in order to vary the coupling and collect the voltage induced at the corresponding winding terminals.
These inductive transducers are generally realised in systems having a logic computing unit which digitally processes data and it is consequently necessary to introduce an intermediate circuit performing the transformation and conversion operations for processing by the computer.
The main object of the invention is to provide such a circuit in simple form leading to greater compactness and reduced weight and, as will be shown hereinafter, providing greater reliability. These properties are particularly advantageous in producing a system of electrical flight controls in accordance with a particularly advantageous application envisaged for the invention. Other advantageous applications of the invention include the digital control of machines.
The conventional solution for the processing of cyclic signals V.sub.M and V.sub.R from different transducers consists of firstly transforming them into continuous signals. For this purpose, each signal is applied to a demodulator circuit which performs a peak or surface demodulation and which is followed by a filter circuit. The signals obtained at the output of the filters must then undergo analog-digital conversion by one of the known processes (coder with successive approximations, coder with single or multiple ramps) supplying the information .theta.R.sub.i given by the ratio between the measuring signals V.sub.Mi and the associated reference signal V.sub.Ri. The different ratios V.sub.M1 /V.sub.R1, V.sub.M2 /V.sub.R2, . . . V.sub.Mn /V.sub.Rn can thus be sequentially stored in a computer memory. Due to the multiplexing of the filter outputs, it is possible to use a single analog-digital coder circuit processing the ratio V.sub.Mi /V.sub.Ri, but which nevertheless forms the most expensive element in the string. Due to the reaction times of the demodulators and particularly the following filters it is substantially impossible to obtain a single channel for the acquisition by multiplexing of these elements and this must therefore be performed as two n independent channels respectively processing the different signals V.sub.M1 to V.sub.Mn and V.sub.R1 to V.sub.Rn.